It is known that barium titanate can only be manufactured by calcining the starting materials BaCO.sub.3 and TiO.sub.2 and also by pyrolysis of metalloorganic complex salts such as barium titanyl oxalate (BTO) or barium titanyl citrate.
According to a method known from J. Res. Natl. Bur. Stand. (1956) Res. Paper No. 2677, pp. 289 to 291 barium titanyl oxalate BaTiO(C.sub.2 O.sub.4).sub.2.4 H.sub.2 O can be precipitated from aqueous solutions of titanium tetrachloride (TiCl.sub.4), barium chloride(BaCl.sub.2) and oxalic acid(H.sub.2 C.sub.2 O.sub.4).
In the known process the aqueous solution of TiCl.sub.4 and BaCl.sub.2 is added dropwise to an aqueous H.sub.2 C.sub.2 O.sub.4 solution having a temperature of .apprxeq.80.degree. C. while stirring vigorously. In order to obtain a stoichiometrically well-defined final product of the composition BaTiO(C.sub.2 O.sub.4).sub.2 .4 H.sub.2 O, the quantities used must be such that there is a barium excess of .apprxeq.1 mol. % and an oxalic acid excess of .apprxeq.10 mol. %, both relative to the molar quantity of titanate.
In this case the precipitate is of a typical)) ((coarse crystalline form with particle sizes in the range from .apprxeq.15 to 70 .mu.m. When the specifications are adhered to, the barium/titanate ratio of the powders manufactured according to the known method is from 1:1 to 1:1.01.
When the barium titanyl oxalate is calcined in an oxidizing atmosphere, for example in air, at a temperature of 1000.degree. C., coarse grained BaTiO.sub.3 aggregates having a grain size from 10 to 50 .mu.m are obtained. The BaTiO.sub.3 primary particles which make up the aggregates exhibit a grain size distribution in the range from 0.3 to 1.5 .mu.m. At higher calcination temperatures the primary particles exhibit a substantial grain growth.
It is known that the shape and the size of the aggregates are the all-important factors with respect to the grindability and that the shape and the size of the primary particles are the decisive factors with respect to the sinterability and chemical reactivity with additives of any type.
It is an object of the invention to provide BaTiO.sub.3 powders which relative to the known BaTiO.sub.3 powders exhibit a smaller sintering interval and hence an improved sinterability; which exhibit an improved reactivity with additives which are added to ceramic masses on the basis of BaTiO.sub.3 to obtain sintering products having desired technical properties; and which can more readily be ground, such that a desired grain size and grain size distribution can be obtained.